The present invention relates generally to countersink tools, and more particularly, to a countersink tool assembly for chamfering bores in rounded parts.
Many machined parts require that drilled holes or bores be countersunk. A countersink or "chamfer" is a frusto-conically tapered enlargement at the opening of the hole which is adapted for receiving the head of a fastener, for receiving a center, or for deburring the hole itself. The tapered surface is concentric with the hole and extends at an angle of less than 90.degree. to the center line of the hole. Typically, holes are countersunk in one of two methods. According to the first method, the holes are first drilled and then countersunk or "chamfered" with a separate countersink tool. The second method employs countersink tools which are a combination of a twist drill and a countersink tool. As such, both the hole and the chamfer are cut during the same operation.
Unfortunately, a common problem associated with countersinking holes drilled into a rounded surface is that the resulting chamfered surface has an irregular cross-section around the circumference of the hole. Therefore, a drill operator must manipulate the countersink tool with respect to the centerline of the hole for changing the angular relationship therebetween in an effort to compensate for the rounded surface contour. Such manual manipulation is undesirable in that the countersunk surface has poor dimensional accuracy and cannot be repetitively produced in an automated manufacturing environment.
Accordingly, the present invention overcomes the disadvantages associated with using conventional countersink tools and provides a countersink tool assembly adapted for cutting a tapered countersunk surface having a generally uniform cross-section around the entire circumference of the hole.
More specifically, the countersink tool assembly of the present invention which is rotatably driven by a conventional drill apparatus, includes an insert having a central aperture and two diametrically opposed ears which extend into the central aperture. A multi-fluted countersink tool is concentrically mounted within the aperture such that the diametrically opposed ears extend into the flutes of the countersink tool at a desired axial location. The ears are adapted to engage and follow the contour of the curved outer wall surface which concentrically surrounds the hole. As such, the countersink tool assembly translates rectilinearly with respect to corresponding changes in the curved contour of the outer wall surface. In this manner, holes drilled into spherical, cylindrical or other curved surfaces can be countersunk to produce a uniform conical chamfer around the entire circumference of the hole.
Additional objects, advantages, and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.